Feinberg et al. taught a combination padlock in their U.S. Pat. Not. 3,720,082 issued on Mar. 13, 1973 as constructed by multiple dials, and multiple sleeves rotatably mounted on a shackle enabling the changing or setting of a lock combination, which however has the following defects:
1. The shackle 50 is locked by limiting the sleeves D as obstructed by several extensions 84 formed on the casing. Each sleeve has only a "single point" on its perimeter resiliently acting on each extension 84 as tensioned by the spring F, to thereby possibly be sensed after repeated trials by an intruder's feeling to open such a lock easily, especially by an experienced theirf.
2. All the sleeves are rotatably mounted on the shackle as retained between an upper retainer 64 and a lower retainer 62 to thereby increase their assembly difficulty and to cause their operation inconvenience, since the looser fixation of the two retainers 64, 62 may influence the precision for uncoupling the sleeves from the dials when setting a new combination, whereas too tight fixation of the two retainers may cause the common rotation of two or more neighboring dials frictionally contacting with each other to influence the dialing operation.
Even a latching device and combination locking means was disclosed by the same inventor in his U.S. Pat. No. 4,327,566, such a combination lock is especially suitable for locking a brief case, but still has the following defects:
1. Upon the changing or setting of a new combination, the button 60 is depressed toward B2 to uncouple the sleeves from the dials for setting a new combination and then recovered to its original position. Since such a linear movement of the button 60 and shaft 20 is easily done, any incidental contacat of the dials may change the combination to confuse the owner if he forgets to memorize the new set combination.
2. A latching piece 10 must be further provided besides the shaft 20 to lock the eyepiece to increase their production cost and operation inconvenience.
The present inventor has found the defects of conventional combination lock and invented the present padlock with projected shackle.